Mooy joined the Seagulls on a one-year loan deal after signing a new contract with Huddersfield Town until 2022 overnight just before the transfer deadline.
Brighton have been interested in the Australian midfielder for several years, and finally secured his signature.
Mooy, who played 90 minutes in the Terrier’s 2-1 loss to Derby County on Monday in their Championship opener, now gets to return to the Premier League.
Ryan, who attended the same school as Mooy in Fairfield in Westfield Sports High School, is excited to have the 28-year-old join him at the Amex Stadium.
“But we all know what a quality player Aaron is," the goalkeeper told The World Game.
“He’s a welcome addition for sure. He’s proven at this level before with Huddersfield and we all see being Aussies what he’s capable of.
“I’m sure he’s a welcome addition.”
Ryan is preparing for his third season in the Premier, after joining Brighton from Spanish side Valencia in 2017.
The keeper was an ever-present force for the Seagulls last season, making 34 appearances and notching six cleansheets, as his club just managed to avoid the drop.
Brighton finished 17th spot in 36 points, just two points above relegated Cardiff City, but it cost manager Chris Hughton his job. Hughton was sacked in May and has been replaced Swansea City boss Graham Potter.
Ryan admits he was “shocked” to see Hughton depart, but has been refreshed by the more progressive and possession-based style new manager Potter is implementing.
“The more points you get earlier on in the season you’re mathematically safe earlier, the easier it is,” the 27-year-old said.
“It got down the wire there last season, as it did in our first season. It came as a bit of a shock that the club relieved Chris from his role.
“But us as players, it’s our industry we’re in and we have full faith in the club and in the people, the directors and everyone who are making the decisions with the club’s best interests at heart.
“I’ve always have the uptmost respect for Chris as a manager and as a man. He was successful in what he did and where he took the club from and to.
“We’re always just now embracing the change because there is no other alternative. Everything moves on and you just have to adjust to these sorts of changes and do the best you can do as an individuals to keep contributing to the team.”
Potter has never managed in the Premier League before and has spent most of his nine-year coaching career with Ostersund in Sweden. The 44-year-old took Ostersund from the fourth-tier into the Allsvenskan and a famous 2-1 win over Arsenal at the Emirates Stadium in the Europa League.
Ryan likens the footballing style Potter is implementing at Brighton to what the Socceroos have employed under Ange Postecoglou and Graham Arnold.
“He’s very approachable as a person,” he said.
“Any queries or questions as players he wants us asking amongst the group. He wants everything clear. In terms of style, he’s very similar to Ange and Arnie actually.
“He wants to play out from the back and an aggressive style of game defensively as well with high pressing. He’s a very much a younger manager and is trying to adopt this modern way of playing.
“He’s very similar to that of Gareth Southgate with the national team as well. It’s been refreshing to have this new approach and new philosophy coming in, it’s one I can relate to quite a bit with my time in Belgium and in the national team with Ange and Arnie.
“I’m looking forward to this season as so far the progress has been there for us as a group. It’s creating a lot of excitement moving forward.”